Reference is made to the co-pending patent application of L. L. White, et al., entitled "Novel Drill Bits Utilizing Polycrystalline Diamond Grit", U.S. Pat. Application Ser. No. 262,910, filed Oct. 25, 1988, now allowed and M. E. Deakins, et al., entitled "Novel Sawblade Segments Utilizing Polycrystalline Diamond Grit," U.S. Pat. Application Ser. No. 262,405, filed Oct. 25, 1988.
The present invention generally relates to improved grinding tools and, more particularly, to grinding wheels containing polycrystalline diamond or cubic boron nitride (CBN) grit (i.e., superabrasives) as the abrasive material.
It is well known in the art to adhere diamond and cubic boron nitride crystals to a support base useful for grinding operations via matrices formed of sintered metals, resins, or vitreous materials, or by electroplating the support base and thereby encapsulating the abrasive grit in the process. Basically, the procedure for adhering superabrasive particles to a support base by sintered metals or resins are similar. The superabrasive particles are intimately mixed with powdered metals or resin powders. The combined powder and superabrasive particles are compressed into a briquet over the support base and the powdered mixture is then heated in a furnace or a heated mold at a temperature sufficient to fuse the resin or to sinter the metal powder into a rigid mass. Either of these matrices form only a mechanical bond with the support base.
Vitreous materials are generally glass-like and powders thereof are mixed with the superabrasive particles and are pressed in a usable form over the support base and then heated, causing the glass to fuse to the support base and the superabrasive particles.
In the electroplating procedure, superabrasive particles are held close to the support base and are immersed in one of several standard plating baths. The support base acts as the anode and a metal such as nickel or copper acts as the cathode. By the electroplating technique, a mixture of plated metal encapsulates the superabrasive particles and at the same time adheres to the support base.
Typically, the diamond or CBN particles are single crystals, however, U.S. Pat. No. 4,776,861, assigned to the same assignee as the present invention, teaches that diamond or CBN polycrystalline abrasive grit useful in tools for grinding can be made by size reducing and leaching non-superabrasive material from a larger polycrystalline compact.
Such polycrystalline abrasive grit is similar in many respects to the thermally stable porous compacts described by Bovenkerk, et al., in U.S. Pat. No. 4,224,380, also assigned to the same assignee as the present invention. In addition, Gigl, et al., teach in U.S. Pat. No. 4,738,689, assigned to the same assignee as the present invention, that enhanced oxidation resistance can be imparted to porous, thermally stable products by coating the exterior surfaces thereof with a metal or the like. All of the foregoing patents are incorporated by reference into the present disclosure.